Various structures found in society, for example furniture, employ joints in their construction. Furniture is made in a variety of shapes and from a variety of different materials. Furniture may be made from wood or metal in addition to being made of less traditional materials such as plastic. While providing advantages such as cost, the use of plastic in furniture challenges the furniture designer in assuring the resulting product is both structurally sound and aesthetically pleasing.
Joint assemblies in furniture that are made from non-traditional material typically include two members that are connected to one another. The first member may be tubular shaped and may be the leg of a chair while the second member is also tubular in shape and is a cross-support of the chair. The cross-support may be attached to the leg at a right angle to form a T-shaped joint. The cross-support is usually shaped on one end for mating with the leg and is attached thereto though the use of an adhesive. Although the leg and cross-support may be solid members, it is sometimes the case that these components are hollow such as when polyvinyl chloride tubing is employed. Here, the leg and cross-support are tubular components that have smooth inner surfaces.
Joint assemblies as the ones described are usually reinforced in order to withstand stresses that are imparted thereon during use. A reinforcing member, such as a wire, may be located inside of the hollow interiors of the leg and cross-support and urged against their interior surfaces. Additionally, liquid polyurethane foam may be introduced into the hollow interiors of the leg and cross-support to cover the reinforcing member. The liquid polyurethane foam expands and hardens into a rigid structure when set. In alternative arrangements, the polyurethane foam employed may not be completely rigid when set in order to make the resulting joint assembly less susceptible to damage by impact forces. The reinforcing member and polyurethane foam work in combination to strengthen the joint assembly to prevent damage when forces are applied thereto.
It is sometimes the case that reinforced joint assemblies as the ones previously described fail during use. It may be that the polyurethane foam becomes separated at one or more locations to the inner surfaces of the leg and cross-support. Also, the polyurethane foam may separate from the reinforcing member. Separation of the polyurethane foam may be caused through normal use of the furniture or through the application of other more significant forces on the joint assembly. Lack of adhesion between the foam and the inner surfaces and/or reinforcing member can lead to failure of the joint assembly as the components will no longer function as intended so that stress concentrations will occur at certain locations. As such, there remains room for variation and improvement within the art.